Method of separating constituents of mineral oils



July 8, 1941-` E. M. DoNs ETAL 2,248,220

METHOD OF SEPARATING CONSTITUENTS OF MINERAL OILS Filed May 26, 1938 3 Sheets-Shag?. 2

I I I I I I I I I I I I I I I I I I 7 I I A I I I I I I I I 'I I I I I I i I i Patented July 8, 1941 METHOD OFv SEPARATING CONSTITUENTS OF MINERAL OILS f Eddie M. Dons and OswaldG. Mauro, Tulsa, Okla., assignors to Mid-Continent Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Application May 26, 1938, Serial No. 210,192

Claims.

This invention relates to methods of separating constituents of mineral oils, and more particularly to the use of selective solvents in counterow systems wherein the solutions are divided into separate layers which flow in opposite directions.

Prior to this invention, the usual object has been to most effectively separate the undesirable constituents from the oil charge in an economical manner, while providing convenient control of the numerous successive conditions which occur in the counterowing streams. This old ob.- ject has led to many different variations of the true counterflow system.

To control the successive operations, various combinations of batch and counterflow systems have been proposed. To provide for controlled continuousoperation, a combination of mechanical mixers and a series of settling chambers alternating with the mixers, have been associated with separately regulated auxiliary extracting apparatus, the object of such combinations being to most effectively utilize the solvent and at the same time control the successive steps of the procedure. 'I'he old apparatus of this kind is complex and quite expensive. It provides for separate control at several stages of the continuous operation, but so far as we are aware, it has failed to most effectively accomplish the desired results.

The effects of temperature changes are fairly well understood, and the old complex systems herein referred to include diierent kinds of equipment to be operated at diierent temperatures. However, these prior disclosures lack the desired simplicity and do not set forth amethod of obtaining the maximum efficiency from the solvent.

A true counterow system, wherein the oppositely flowing layers contact with each other has been regarded as an uncertain4 method, lacking any positive control at the successive stages, although it has the advantage of simplicity not found in the previousV use of mechanical mixers alternating -with settling chambers. Heretofore, the use of various different kinds of expensive devices and` apparatus has been regarded as essential to provide the desired control.

One of the objects of the present invention is to most effectively accomplish all of the desired results in a simple counteri'low system, lacking the various different types-*of separately `regulated mixers, settlers, etc., heretofore employed to control the procedure. l

A separate and distinct object is t0 provide a series of diierent zones which result in a substantial improvement, and which may be' advantageously employed in any oi the various types of counterflow systems, including the simplest type wherein the counteriiowing layers are in direct contact with each other, as well as the complex systems, involving the use of kseparate mixing and settling chambers.

More specifically stated, an -object is to produce a system including artificially cooled Vsaturating and precipitating zones near oppositeends ofthe system, with relatively hot scrubbing and refluxing zones between said cooled saturating and precipitating zones. In the preferred. form of the invention, the several zones are in free lcommunication with each other and so arranged that the raiiinate is discharged from the cooled precipitating zone atV one end of the system, while the extract passes from the cooled saturating zone near the opposite end. Y y

Despite theold objections to lack vof control in a true counterow system, and the previous failures inv attempts to accomplish the optimum results in complex combinations of different kinds of apparatus, we will hereinafter set forth details showing justhow to produce an extract approximately saturated with the lowest grade constituents,` while discharging a raffinate containing very little if any excess solvent, and free of other. undesirable constituents. f Specific examples will show how the series of zones may be employed to economically accomplish all of these results in a simple counterflow system. In view of this disclosure, it will be apparent that a system of this kind can be veryveasly regulated to economically producethe highest vgrade lof rainate andV the lmost .degraded extract,l or any desired intermediate grades with a corresponding degree of economy. The cooperative functions in the several zones may be determined by simple preliminary adjustments and, thereafter maintain without further attention aside from the routine observation of temperatures, etc. f

With the foregoing and other objects vin view,

vthe invention comprises the novel method hereinafter more specically described and shown in the accompanying drawings, which illustrate one form of the invention. However, it is to be understood that the inventioncomprehends changes, variations and modications within the scope oftheclaims hereunto appended.

Fig. -1 is a side view of an extracting column embodying features of this invention.

in Fig. 1.

Fig. 3 is an enlarged diagrammatical view, with arrows indicating the counterowing streams contacting with each other and moving in intersecting paths while iiowing from one elevation to another.

Fig. 4 is a section on the line 4-4 in Fig. 3, with arrows indicating the radial counterflow which occurs between the intersecting paths.

Fig. 5 is an enlarged section illustrating zones near the upper portion of the extracting` column.

Fig. 6 is a view similar to Fig, 3 illustrating another type of counterflow.

Fig. 7 is a diagrammatical view pointing out conditions which may be maintained in the several zones.

To illustrate a simple system embodying the several features of the invention, we have shown -acounterflow v4system 4comprising :a single verticalccolumn whereinall of the successive 'operfations. are :performed,and without lin any way limiting thepatentftozthis specific example, the detailsiiappearingfin fthe drawings .will be defscribed as :follows:

fl designates la vertical extracting `column having an inlet pipe 2:-nea-rthe topifor-thecontinuousg admission `of a stream of selective solvent, and 4:anzinlet pipetgnear the bottom Vfor the admission'gof :arcontinuous stream of oil tobe acted Suponzby'the solvent.' The degradedfextnactmay ibe?continuously:discharged through Ia pipe 4 leading'lrfom-'the lower portion of the column, while `the railinate is continuously dischargedthrough a pipe f5 leading .'l'om the upper portionof the column.;4 v

. 'I-hefrsystem -herein `shown is provi-ded with .a series fof lsuccessive zones V.vs/herein varying, conditions are deliberately Amaintained,seas-.t0 Provide .for'very -eii'ecti-ver` action at each of thefnu- -merous stages ofthe extracting operation. These zonesmay'be located one above the other as :shown ,in the drawingsor arranged in anyother suitable 'mann-er. .Before describing Athe vari- ,ous conditions, Vwe -will briefly state that .thezones .herein `shown include aprecipitatingzone at ,the `topQof the column,asettling zonebelow thepre- ,cipitatingf zone, aA solvent `zone` below said settling zone, a scrubbingzonebelow said vsolvent zone, a refluxing. z one below the scrubbing zone, asaturatingzone below said .refluxing zone, and a saturated releasing zone below said saturating zone. l.

LTo divide the. solutions into numerous counterjflowing. l layers 'cont-acting with each other, the interior "of the apparatus may include a series -ofialternating baille plates E and 1, as shown in 'Figures-5 2, 3-and 4. Each baffle Shasaperipheral edgejseparated Vfrom the inner face of the col- *Eachbaillej'l hasja peripheral edge suit- `ably unite-d with the inner face, of the column, and a central ropening 8 Athrough which the counterowing solutions fv oil Aand solvent rise and fall in passingfro-m one of the baille plates 'toanothen The paraffinic constituents of the oil charge gradually-advance toward the top of the extractfing Ycolurnr-i, while the naphthenic constituents are gradually' dissolved Vin the solvent to produce heavierjsolutions which lflow Y'toward the bottom lofsaid column f By referringto Figures 3 and 4 it will 'be un- Alderstood that ithelsolutionsof oil and solve-nt are divided into numerous-thin layers of different spe- Fig. 2 is a vertical section of the column shown cific gravities contacting with each other. These contacting layers move radially in opposite directions, and at gradually changing speeds, toward and away from the central portion of the column. The highest speed is attained near the central V portion of the column where all of the liquid must pass through a relatively small openin-g 8, while the lowest speed'is near the periphery where approximately the same volume of vliquid flows through a much larger' opening between the periphery of a baille plate 6 and the inner face of the column.

Mixing zones are formed at the central openings 8 Where the oppositely moving layers travel inintersecting paths from one plane to another at a relatively high speed. The resultant mixtures are permitted to settle yand stratify at lo-wer speeds around the central mixing zone, `the speed of each layer being gradually increased as it moves toward the central mixing zone and gradually decreasedas it moves away from said mixing zone.. The oppositely moving layers also travel/through Yintersecting paths in the zones o-f lowestv speed around the peripheries of the baille plates Ali, iso as to provide secondary mixing zones alternating with the primary mixing zonesat the centralportion ofthe column.

r'The solvent is thus combined with oil that -en-ters'at theilower portion of the column to profand 'these yplates are staggered to provide a tortuous ypassageway for the counterowing solution's.

However, advantages are gained yby arranging vtheA baille plates `as shown in Fig. 2. Attention i-s directed to the varying spaces between the fbaile plates 6 and 1 in this view. The adjacent plates are comparativelyV far apart near the bottom of `the column, and substantially closer to each other near the top of the column, the disltance between said plates being progressively decreased to-ward the top of themcolumn. This arrangement progressively decreases the thicknesses of the liquid streams passing from naphthenic phasesin the lower portion of the column to moreV paraflinic phases at higher elevations. "The lowest velocities will occur in the thickest layers, and th-ejhighest velocities in the thinnest layers, so the yarrangement just referred towill result in a progressive increase in the velocity of :the rising streams, 'and a corresponding `decrease inthefvelocity of the descending streams. Consequently, the most drastic treatment will occur -in the -scrubbing zone where the extremely thin counterowing layers are moving at the highest velocity, and substantially different conditions are produced in each of the other zones.

lSuch vconditions are deliberately varied to selectively produce Vdiilfe're'nt treatments in the several zones, the object being to provide for a ,high degree of efliciency at each of ithe numerous stages.

Aside from the velocities and the thicknesses oi.' the counterflowing layers, the eifect of the treatment at any givenpoint will depend partly upon the temperature at that'point. As an "illustration of suitable temperaturel regulating devices, We have shown coolers III 'in the precipitating zone, heaters l2 at the scrubbing zone, coolers I3 in the rei'luxing zone, a cooler I 4 at the top of the saturating zone, andv coolers I5 in the saturated releasing zone As an aid in describing one form of the invention, and without in any way limiting the invention .tospecific temperature conditions, we have indicated a series of temperature variations in Fig. 7. Using these speciiic temperatures merely .for convenience in explaining conditions which may be established land maintained in the different zones, we will briefly refer to each zone, as follows:

The saturating'eone The oi'l to be extracted may be introduced near the bottom of the saturating zone at a temperature of 60 F. In this zone, the .bailies 6 and 1 are spaced apart to provide relatively low velocities in the counterflowing layers. The descendin-g solvent streams, or layers, contact with the rising mass o-f fresh oil. VAssuming that the object is to saturate the outgoing solution with the most degraded naphthenio components' at a temperature of 60 F., the saturating zone Vmay be maintained at aboutv 60 F. The low velocity and low temperature are prolonged, and the most soluble (naphthenic) components of the incoming oil 'are very readily dissolved in the descending solution, while the lighter, more paraflinic portions rise into the less saturated zone.

A study of the conditions in this saturatiner zone vwill show that the most degraded naphthenes of the incoming oil arequickly dissolved by the descending solvent, and as the saturation progresses, the less degraded compounds are thrown out of the degraded solution, 'and transferred to the more paraflnc rising streams. Deliberate saturation of the descending solvent with the most degraded portions of the oil is an important function. It provides for recovery of approximately all of the desired paraffinic compounds in the original oil.

However, it is to be understood that there is no exact line of demarcation between one zone and another, and 'even when thev descending solvent is perfectly saturated with all of the vmost degraded components of the original oil, the saturated solution may contain entrained parainic particles having substantial value. Therefore, advantages are gained by Atransferring the saturated, or approximately saturated, solution to another zone which will beA briefly described as follows:

The saturated releasing zone The solvent, approximately saturated with the most degraded components of the oil, descends from ,the saturating zone to the cool saturated releasing zone.y The velocity inthe last mentioned Zone is extremely low, a large body of the approximately saturated solution being maintained between the bottom of the` saturating zone and the outlet for degraded extract. These conditions are most favorable to complete saturation, and they positively provide for release ofentrained parafilnic compounds, which slowly rise to the surface of the saturated releasing zone,. and enter into the rising parafnic stream. Paraining material is thus recovered as part of the valuable parafllnic oil, instead of being carried away in the degraded extract. v

The refiuxingzone After the most soluble (degraded) portions of the incoming oilare transferred to the descending solvent in the saturating Zone, the less soluble (more paraffinic) portions rise into the bottom of the refluxing zone. At this stage, more drastic treatment is required to produce the desired separation. The temperatures of the rising stream my be progressively increased in the reuxing zone, and the velocities of said rising stream may be increased las suggested by the baille arrangement in Eig. 2. Opposite conditions appear in the descending solvent stream, wherein the temperatures and velocities are decreased toward the bottom of the reuxing Zone.

This combination of conditions establishes an internal reflux wherein semi-naphthenic portions of the descending stream are transferred to the rising parafnic stream. The descending naphthenic stream progresses through more saturated conditions at gradually decreasing temperatures, so thek least soluble portions of the descending naphthenic stream are positively discharged to the rising parafnic stream. The free interchange of higher and lower grade naphthenes transmits the intermediate grades to the rising stream, while the descending stream becomes more saturated with ,the lower grade.

In this refluxing zone there is a dispersion of charging stock in a semi-saturated `solution-of naphthenic compounds, Ias distinguishedl from .a true solution. There is a concentration of naphthenic oil andan interchange which sifts out the higherk grade naphthenes andl permits them to r-ise in the column, while the most degraded portions are retained in or-transferred to the descending stream. The cool incoming oil is not immediately dissolved. The most soluble portions are quickly dissolved in the saturating zone, but a substantial portion of the semi-paraffnic solution then rises in globules tothe refluxing zone, which immediately starts the recycle. A

The interchange in this refluxing Zone can be v ery effectively obtained by progressively increasing the` temperatures and velocities of the rising stream, while decreasing the temperatures and velocities of the descending stream, at the same time frequently mixingA and settling the counterowing streams. However, the invention is not limited'to this lspeciio combination of details in the `refluxing zone.

Y The scrubbing zone The solvent zone The fresh solvent enters near the top of the scrubbing'zone, anda body of the solvent may vbe permitted to accumulate in the higher solvent zone. In the specific example herein considered, the selective solvent is relatively heavy, and it selects the heavynaphthenic components of an oil. The body of solvent in the solvent zone may be at a relatively high-temperature conforming .approximatelyto theztemperature in thescrubbing zone. Under these conditions, 'the light solution passingfrom the top of the scrubbing zone -will freely rise through the body of heavy solvent .and enter into the next higher zone.

The higher Vsettling zone Ihe velocity in this settling zone is very low, and though the temperature may be high, aportion of the entrained solvent Ais permitted to settle from the rising solution and` return to the next lower zone.

The precipitating zone Deliberate cooling of the solution rising to this zone, coupled with low velocity in the relatively large body of solution, precipitates .excess solvent, including entrained solvent particles. The precipitated solvent ventrains in solution Within itself the semi-naphthenic components residually left in the parafnic solution, and this material is returned to the lower` Zones, instead of passing out Withthe paraflinic solution.

The products Approximately all of the desired parafnnic components are carefully separated from the othercomponents and discharged from the top of the'cool precipitating zone, free of excess solvent and likewise free of contaminating degraded particles. .A predetermined refined parafiinic so'l lution is thus recoveredfrom the system, and the relatively small .percentage of solvent can be readily distilled'from the parainic oil.

vThe extract discharged4 from the bottom of the column is approximately saturated with the most the numerous varying intermediate conditionsv are quite different from the rather haphazard conventional ideas of. merely mixing and settling successive solutions. In'any extracting process of this kind, `the composition is undergoing constant changes, beginning with the initial solution of raw oil yand solvent, and very gradually progressing through numerous -stages Iwhich -ultimately provide a degraded solution and a radically different refined solution. The numerous diiferent intermediate conditions are deliberately established to produce amost eifective treatment in the combinationof zones,and also at the successive stages in each-zone.

Furthermore, all of. the numerous special .results can be very conveniently accomplished, and accurately controlled, in a simple counterow system, lacking the variousmechanical .appliances, and elaborate apparatus ordinarily employed to provide a few of the desired special conditions.

As a specific example, we Will referto results obtained while operating under temperature conditions approximately asshown in Fig. '7 vofthe drawings. The originaloil was a petroleumlubricating stock having an A. .P. I. gravity of 23.9 and consisting of ablend ofresidue and-distillate, known as Ybright stock.` Dichlorethyl: ether Awas employed as the selective solvent, vusing Iabout three .parts solvent to onev part of the original oil. The .resultantdegradednaphthenic solution -oil and :9% solvent.. tion contained 73.4% ofthe original oil stock, and

-contained'x26.6% ofthe original oil-stock, but this degraded f solution .as a whole -consisted. yof 9.1%

The paraliinic oil soluthis solution as a whole consisted of 85.4% oil and;14.6%lsolvent. Therecovered paraffinic oil had-an I A. 1P. I. gravity of.` 27.8 and a viscosity index of 98.8.

In another specific example, the original oil stock-was a waxy lubricating oil distillate having -anA.-P. I. gravityof 23.9:and a viscosity index of 62.4. YDich'lorethyl ether was employed as the selective solvent, using about 1% parts solvent to 1 part of the originalV oil stock. The resultant degraded naphthenic ysolution contained 33.8% of the loriginal stock, but this'degraded solution Vasa fwhole consisted of.18.3% oil and v81.7% solvent. The parafflnic oil solution contained 66.2% of the originalstock, and this solution as a whole consisted of '78%'oil-and-22% solvent. The recoveredparainicoil hadanA. P. I. gravity of 30.6 andA aviscosity `index of111'8.

The systemfcan be-very leasily regulated to economically producethe veryhighest grade of rafnate and -the lowest 'grade of extract, or any `desired intermediate grades-can be obtained with a corresponding Vdegree ofeconomy. In `other Words, afsystemofthis kind isv quite flexible and the several conditions can-be easily varied to ob- .tain the products ymost Ydesirable under varying marketconditions. `Any suitableselective solvent maybe used .to `extract"lubricatingoil stocks as wellas `numerous other l.kinds ofvoils, and any V.desired temperatures-may bev employed. There- Ifore,` it is to `beY understood .thatthe invention is not vlimited .to the.specc-examplesfherein set forth, ,nor to any ofi-the vspecific combinations of conditions, .except as specified` in the claims.

yAfter .the..predeterminedV operating conditions have been established,` the .system can-beopera ted continuously. with verylittle attention upon the part ofthe operator, aside from routine observations.

To 4compensate for accidental or incidental variations which may .occurfrom time to time, or to avoid unnecessary immediate attention to such variations, -we have shown how an abnormal condition at -one .point in the `system may -be temployed in regulating the flow through the sysem.

As an illustration of one form of this feature, attention is directed to the 'float I6 shown in Figures 1, 2 and'5. This float is secured to a pivot rod I1 extending through'the column and provided with an external arm I8 connected to a valve I9. Air under pressure is transmitted to said valve -l`9 from an air supply pipe 20, and

such air pressure may be transmitted through vthe valve |9 to a pipe 2| leading to a pneumatic valver 22 'in the 'discharge conductor 4 leading lfrom theY bottom `of the extracting column. These lby such regulation, one should observe certain conditions existing in the portions of the column shown by Fig. 5.

This View illustrates several conditions at the upper portion of the extracting column, including the cooled precipitating zone, the warm settling zone, the warm solvent-zone, and the v,top

atively heavyv body of liquid below the light paraflinic oil solutions in the higher zones. 'I'he heavy solvent body should not be permitted to rise through, or into, the precipitating zone, one of the objects being yto exclude excess solvent from theoutgoing raiiinate.` Y

Y In actual practice, there is a line of demarcation, or interface, between the body of heavy solvent and the next higher body of parainic solution.

VTo positively exclude the heavy body of solvent fromY the precipitating zone, and to maintain said interface at a. desired elevation below the cooled precipitating zone and above the hot scrubbing zone, the float rises and falls in response to vvariations in the level of the interface. This float movement regulates the discharge of naphthenic solution (extract) from the lower portion of the column.

The incoming stream of fresh solvent and fresh oil, and also the heating and cooling, may be regulated as desiredr to yproduce the highest efficiency at each stage of the several zones. Thereafter, accidental orV incidental variations will be compensated Vfor by the float-controlled valve which regulates the discharge of the extract in accordance with conditions existing in other parts of the system, thereby maintaining the desired conditions at Aopposite ends of the system, regardless of such accidental or incidental variations.

For example, if the, discharge of degraded extract is not sufficiently rapid, ank excess of liquid will accumulate in'the column, thereby increasing the elevation of the `'interface at the top of heavysolvent zone. The float will then rise to increase the discharge of degraded extract. Or, if the discharge of said extract is too rapid, the float will fall and thus decrease said discharge. On the other hand, if the discharge of light raffinate from the top of the column is too rapid, the body of solvent inthe solvent zone will rise in the settling zone. It will be observed that the light globules of f, par'afliniic solution, vrising through the solvent zone,'contain the most insoluble portions of the original oil, so this material is not dissolved by the large body of 4solvent in said solvent zone. However, the rising globules will carry entrained solvent into the next higher settling zone, where the low velocity permits'. free settling of heavy solvent particles, which return to the solvent zone. A more drastic separation occurs in the higherprecipitating zone where the deliberate cooling releases a substantial portion of additional solvent, which also returns to the solvent zone with residual seminaphthenic components. Such residual components are thus returned for further treatment, instead of being permitted to 'escape with the outgoing paraiiin'ic solution; .n

We-claim:` L i 1. In the art of usingselective solvents to Vvseparate constituents of mineral oils, the method which comprises maintaining in a ycontinuousv counterflow system a series of zones including a precipitating zone, a scrubbing zone,"a reuxing zone, and a saturating zone, transmitting the selective' solvent into said scrubbing zone, introducing the mineral oil into said saturating zone, discharging, the approximately saturated extract solution from said saturating zone, .discharging the raflinate fromsaid precipitating fzone, dividing the intermediate solutions into numerous toward the top of the column, thereby moving the float to increase the discharge of extract at the bottom, which will relieve the excess, and

prevent accidental discharge of fresh solvent in the outgoing rened raffinate.

Similar results can be accomplished by regulating the discharge of raffinate, or by varying the admission of fresh oil or fresh solvent. However, the foregoing illustrates one form of this feature, which prevents any very serious disturbance due to abnormal conditions which are likely to arise in any extracting system.

In the zones shown by Fig. 5, the liquid in the solvent zone may be almost entirely pure solvent, derived partly from the incoming fresh solvent stream, and partly from the higher zones. The scrubbed paraiiinic solution leaves the top of the scrubbing zone by flowing along the bottom face of the bafe 6 shown in Fig. 5. This light solution rises from the periphery of said baie in the form of light globules which pass through the body of heavy solvent as indicated in Fig. 5, and enter into the body of light parafnic solution counterflowing layers contacting with each other in the refluxing and scrubbing zones'fand lcausing the layers to Yflow in intersecting paths, maintaining the saturating zone at a relatively low temperature topermit free saturationof the outgoing solvent with the most degraded components vof Vthe' oil, vmaintaining the contacting counterflowing streams in said refluxingzone at higher temperatures which increase in the streams passing from the saturating zone to the scrubbing zone and correspondingly decrease in the streams flowing toward said saturating zone, maintaining the counterflowing streams in the scrubbing zone under prolonged yhigh temperature conditions to provide time Afor the heated solvent to blend. with the oil and dissolve intermediate components, transferring: the Vrafiinate A'stream from the top of said scrubbing zone to said vprecipitating zone, and maintaining said precipitating zone at a .temperature substantially lower than the temperature of said scrubbing zone so as to separateentrained solvent and residual compounds from the outgoing raffinate stream.

2. In the art of using v'selective solvents to separate constituents of mineral oils, the method which comprises maintaining in a counterlow system fa series of zones including a precipitating zone, ascrubbing zone below said precipitating zone, a refluxing zone below said scrubbing zone, and a saturating zone below said reuxing zone, continuouslyv transmitting the selective Vsolvent into said scrubbing zone, continuously transmitting the mineral oil into a lower zone, dividing the resultant solutions into counterilowing streams contacting with each other in said scrubbing zone-and refluxing zone, discharging the lightest solution from said precipitating zone, while discharging the heaviest solution from a zone below said refiuxing zone, maintaining a relatively high and approximately uniform temperature in said scrubbing zone while causing the counteriiowing streams therein to flow in intersecting paths, deliberately cooling said precipitating'zone'to return aportion ofA the solvent with residual'oil components `to saidscrubbing zone,` progressively Vdecreasing the temperature o f theA descending streams YinV said refluxing zone while increasing the temperature of the rising vstreams in the same zone and causing the different streams to flow in intersecting paths in said reiuxing zone, transmitting the heaviest portions of the Vdescending streams into said saturating zone, ,and maintaining a relatively low temperature insaidsaturating zone to produce a solution ,approximately saturated "with the most naphthenic-components of the oil'.

3: In the art of using selective solvents to separate constituents of' mineral oils, `the counterflow.v method which comprises maintaining `in a' continuous counterow systemY a series of zones including a cool precipitating zone,` a hot settling zone below said precipitatingjzone, a `hot solvent zone below said settling zone, and cooler more naphthenic zonesv below said hotV solvent zone, introducing the selective solvent into said sol-vent zone, introducing the mineral oil into one of said cooler zones; discharging the raffinate from'said precipitating zone, discharging the extract from the opposite end of the system, dividing the intermediate solutions into numerous counteriiowing streams contacting with each other, and causingfsaid streams to ilow in intersecting paths, transmitting the rising stream through the hot solvent zone and thence through said hot-settling zone, maintaining a relatively low velo-city in said -hot'settling' zone to freely separate entrained heavy solvent from the rising stream, transferring the rising stream from the top of said Yhotsettling zone to the cool precipitating zone,` and maintaining said cool precipitating'zone at temperatures substantially below the temperatures of the adjacent 1ower zones, so-as to separate excess solvent and residual heavy compounds from the outgoing 'rafnate stream.

4. Inthe art of using selective solvents to separate constituents of mineral oils, the counterfiow method which. comprises maintaining in a-continuous counterflow system a'series of zones including a cool precipitating zone, a'hot solvent zone below said cool precipitating zone, a hot scrubbing zone below said solvent zone, a reiiuxing zone below said scrubbing zone, a saturating zone below said refluxing zone, and a saturated releasing'zone below said saturating zone, introducing the selective solvent into said solvent zone, introducing the mineral oil at a point adjacent to the bottom of said saturating zone, discharging the extract from the saturated rel-easing'zone, discharging-the raiiinate from said precipitating zone, dividing the 'intermediate solutions into numerous counterflowing streams contacting with each other in the saturating zone; refluxing zone and scrubbing zone, and causing said streams to flow in intersecting paths in-each ofthe last mentioned zones, maintaining the -saturating-zone ata relatively-low temperature and lrmaintaining a relatively lowvelocity in said -saturating zoneto permit free saturation of -the-descending solvent with the most degraded components ofthe oil,Y maintaining a low temperature anda still lower-velocity in said saturated releasing zoneto release entrained particlesof paraftlnic compounds fromfrthe outgoing saturated solution, maintaining the con` tactingcounterflowing; streams in said reuxing zone at substantially -higher `temperatures which increase-in the streams -rising toward said scrubbingzone and correspondingly decrease in the streamsdescending toward saidy saturating zone, at thesametime increasing the velocity of the streams progressing toward said-scrubbing zone, whiledecreasing the velocity ofthe companion streams iiowing` toward -said saturating zone, maintaining the contacting' counterowing streams in said scrubbing zone under prolonged high temperature conditions to provide time -for the heated` solvent toblend with the oil and dissolve intermediate components which enter into the descending streams, and progressively increasing-the velocity of the rising streams as they advance towardV the top Vof said hot scrubbing-zoneso-as toincrease the scrubbing action, transferring the rising stream from said hot solvent zone to the cool precipitating zone, and maintaining said: cool precipitating zone at temperatures substantially below the temperatures ofthe adjacent lower zones, so as to separate excess solventand residual heavy vcompounds from the'outgoing, raflina-te stream.

5. In the art of using selectivesolvents to separate Vpaijaiiinicand naphthenic constituents of mineral oils, the counterfiow methodwhich comprises maintaining in a continuous counterow system a ser-ies ofzones including a cool precipitating zonefa'` hot-v solvent zone below said precipitating zone, and cooler more naphthenic zones below saidv hotsolvent zone, introducing theselective'solvent into said Vsolvent zone; introducing the-mineral oil into onefof said cooler zones; discharging'the paraiinic rafiinate from said precipitating-"zone, discharging thenaphthenic extract fromthe-opposite end of the systern, dividing the intermediate solutions into numerous counteriiowingV streams contacting with-eachother, and causing said streams to iiow in intersecting paths, transmitting therising stream through the hot solvent zone and to said cool precipitating zone, maintaining said cool precipitating zone at temperatures substantially` below the temperatures of' said solvent zone, so as to separate excesssolvent and residual heavy compounds from -theV outgoing' raiimate stream, maintaining a substantial body of solvent in said solvent zone; and regulating the discharge of sa-id naphthenic extract in accordance with Variations-in the'level of said body of solvent.

EDDIE M. DONS.

OSWALD G. MAURO. 

